I use it for the first time when I run Mate thing like Firefox bookmark, timezone, way the screen looks and other thing. My question is can I run it again when I add Firefox bookmarks and maybe other stuff?

But will it backup the whole thing or just backup where the other backup stop at? I want to make backup if something goes wrong. I will move all my save data to another USB or Hard Drive. When I make the 2nd backup I will remove the 1st if the whole 2nd gets backup.

I just like Slackware because I think it teach you about Linux to build packages where Ubuntu is like Windows you just install programs you want.

I'm just checking for unanswered questions. If I understood your question correctly and all GUI handle dat containers the same, yes.

Boot the GUI with changes to that dat then when you're happy with it's content. Reboot into Always Fresh and copy the container for a backup image of your current changes.

Example:
1 - Always Fresh - Make dat A, with boot config to use it for changes.
2 - GUI using dat A changes - Make any permanent changes you want now.
3 - Always Fresh - Copy dat A to make dat B.
4 - GUI using dat A changes - Make more changes and use it as a sandbox if ya want.

Now, If dat A breaks. Reboot in Always Fresh and overwrite dat A with dat B. This way you'll have a recent recovery point.

Note, copying a dat while changes are attached will risk corruption to the copied one like it did with me.

I boot with a save.dat file as my normal boot mode and yes it includes new changes together with the previous ones.

I also periodically make a copy of my save.dat file and save it as a save.dat.xzm file. I can then boot without my save.dat file and it's changes=EXIT option and use an extramod= option instead pointing to the folder with my save.dat.xzm file and have all my changes present. And not have to worry about the system being changed. (grandkids)